When a plurality of heterogeneous/homogeneous communication systems operated in the same frequency band are present, a Frequency Hopping Spread Spectrum (hereinafter referred to as “FHSS”) system may avoid interference at high speed using a frequency hopping technique. For example, Bluetooth, which is a kind of FHSS system, reduces the influence of homogeneous/heterogeneous interferences in a band by transmitting signals while performing pseudo-random frequency hopping through 79 channels in the band at a rate of 1600 hops per second. However, when a frequency hopping channel is determined without consideration of an operation environment such as channel status, there is a disadvantage in that, when a plurality of interference signals are present in the same band, performance is greatly deteriorated. In order to mitigate this disadvantage, IEEE 802.15.1 classifies channels on which interference signals are present, and adaptively changes frequency hopping channels, thus avoiding interference in the same band. However, since such a frequency hopping technique checks frequency hopping channels on an FHSS system channel basis, the time required to classify channels is lengthened, thus causing the disadvantage of being able to cope slowly with the same channel interference. Moreover, when channels on which Frequency Dynamic (FD) interference signals are present are excluded from frequency hopping channels, the number of available frequency hopping channels remarkably decreases, and then a problem arises in that the probability of colliding with other FD interference signals greatly increases.
The present invention relates to an interference signal avoidance apparatus and method for an FHSS system, which transmit signals while avoiding interference signals in an environment in which homogeneous/heterogeneous interference signals are present in the same frequency band, and a basic concept thereof is described as follows. The present invention first detects an interference signal and changes the frequency hopping channel of the FHSS system depending on the characteristics of the detected interference signal, thereby avoiding homogeneous/heterogeneous interference signals. The present invention is configured to determine variables of an interference signal detector so that the transmission performance of the FHSS system is maximized while satisfying a detection probability for interference signals to a desired level, to instantaneously estimate whether an interference signal is present on a plurality of frequency hopping candidate channels including a subsequent frequency hopping channel by using the interference signal detector, and to transmit signals through a channel on which no interference signal is detected, thus avoiding homogenous/heterogeneous interferences in the same frequency band. In this case, the frequency hopping candidate channels are established in consideration of the characteristics of a Frequency Static (FS) interference signal, and then the influence of the FS interference signal is minimized. In particular, the present invention is configured such that, when channels on which an FS interference signal is present are detected, transmission performances appearing in a case where those channels are excluded from a set of frequency hopping channels and in a case where those channels are not excluded from the set are compared with each other, and then the set of frequency hopping channels is updated. By means of this operation, the present invention may efficiently transmit signals while avoiding homogeneous/heterogeneous interference signals in the band, even in an environment in which a plurality of homogeneous/heterogeneous interference signals are present.